1. Field of the Invention
The present invention relates to automatic engine control devices capable of controlling an automatic engine stop of an internal combustion engine.
2. Description of the Related Art
Recently, some types of vehicles are equipped with an automatic engine control device. The automatic engine control device controls an automatic engine stop in order to stop an internal combustion engine during an idle state of the engine mounted to the vehicle. The execution of the automatic engine stop decreases a terminal voltage of an on-vehicle battery of the vehicle. Specifically, at the moment when the automatic engine control device switches the state of the engine from the idling state to an engine restart mode, a large amount of current is supplied from the on-vehicle battery to a starter mounted to the vehicle. Such a large amount of current drastically decreases the terminal voltage of the battery, that is, reduces a large amount of capacity of the on-vehicle battery.
As a result, it is difficult for the on-vehicle battery to supply an adequate amount of electric power to the starter when the terminal voltage of the battery is less than a predetermined voltage, it becomes difficult for the starter to restart the internal combustion engine. Accordingly, it is necessary for the on-vehicle battery to keep the voltage of not less than the predetermined voltage during engine idle stop (that is, idle reduction).
By the way, for example, Japanese patent laid open publication No. JP 2002-31671 discloses a conventional technique to judge whether the execution of the engine idle stop control is permitted or not based on various judgment conditions: (1) whether or not a SOC (State Of Charge as a residual capacity, for example) of the on-vehicle battery is not less than a total of a necessary capacity to restart the internal combustion engine and a standard capacity of the on-vehicle battery to be consumed by electrical loads during the engine idle stop.
There is a recent demand for vehicles to execute the engine idle stop multiple times as many as possible, and to extend a period of the engine idle stop from the viewpoint of solving recent environmental issues.